A. Field of the Invention
The invention relates to the field of measuring thickness of materials. The invention relates further to a technique for processing signal data so that a Fourier transform can be performed more successfully.
B. Related Art
Measuring thickness of layers is of particular usefulness in the semiconductor arts.
In the past, people attempted to use rocking curve outputs of x-ray diffractometers to measure thickness of layers. This was a cumbersome process. First, the user would identify bumps in a rocking curve manually and manually put cursors at adjacent maxima. From the position of the cursors, an angle of difference could be derived. From that one could derive a dominant thickness in the material under observation. What layer was dominant at a particular angle would depend on Bragg angle and selection rules. The user would have to guess based on expectations of thickness of particular layers in the material. That guess would be a starting point of simulation. The simulation parameters would then be altered until they produced a simulation curve matching the measured rocking curve.
Some also tried to Fourier transform the rocking curve to yield a thickness curve, but the results were so noisy as to be useless.